Processing of fatty acids and making grease therefrom



Patented Mar. 13, 1951 V UNITED STATES PROCESSING OF FATTY ACIDS AND MAKING GREASE THEREFROM William 1:. Whitney, Bartlesville; Okla, assignor to Phillips Petroleum Company, a corporation of Delaware This invention relates to improved lubricants. In one of its more specific aspects, it relates to a method for improving impure saturated soaps and materials saponifiable by reaction with an alkali base for grease making. In another of its more specific aspects, it relates to a method of improving impure alkali metal or alkaline earth metal soaps of saturated fatty acids.

Lubricating greases are conventionally prepared by the combination of a suitable lubricating oil with a thickening or gelation agent by which the lubricating oil is transformed to a plastic mass. Most commonly used as such thickening-or gelation agents are metal soaps of long-chain fatty acids. such as those obtained from natural sources .or from glyceride-yielding mixtures of fatty acids. The soaps thus prepared are dispersed in lubricating oil to form a ease.

Most naturally occurring fats and oils, or fatty acid mixtures obtained therefrom, contain appreciable amounts of unsaturated fatty acid radicals. Soaps which contain appreciable amounts of unsaturated fatty acid radicals have been conventionally used as thickening agents for greases.

It has been discovered, however, that unsaturated fatty acid radicals have undesirable effects on the resulting grease because they decrease the resistance of the grease toward oxidation. Unsaturated fatty acid radicals also decrease the consistency, work stability, and water resistance of a grease.

An object of the invention is to provide an improved method for processing fatty acidsfor grease making. Another object is to provide an improved method for removing impurities from saturated soaps, and materials sapom'fiable by reaction with an alkali, for grease making. Another object is to provide'an improved method for producing a lubricating grease. Another object is to provide an improved lubricating grease having improved consistency, work stability and water resistance. Other and further objects and advantages will be apparent tothose skilled in the art upon study of the accompanying description and discussion.

Generally speaking, the invention resides in a method of preparing materials for grease making by processing impure saturated soaps or materials which are saponifiable" by reaction with an alkali. By materials which are saponifiable by reaction with an alkali, it is intended to include a pure unsaturated acid or esterof an unsaturated fatty acid. As pointed out above; most naturally occurring fats and oils,

- 'No Drawing. Application June 7, 1948,

- Serial No.31,595

10 clai s. (01. 252-39) or fatty acid mixtures obtained therefrom, contain' appreciable amounts of unsaturated fatty acid radicals. Most of the undesirable impurities in saturated soaps, fatty acids, and fats generally comprise'unsaturated radicals which may be converted to saturated materials or removed from the saturated materials by contacting the" materials with an anhydrous alkali at a relatively high'temperature, and neutralizing th mixture with a mineral acid.

I have found that predominantly saturated fats, fatty acids, and soaps which contain be---@ tween about ten and about twenty-four carbon atoms per molecule may be greatly improved for grease making by contacting the predominantly saturated material'with an anhydrous alkali, which ranges at least ten per cent by weight in excess of that stoichiometrically equivalent to the material treated, at a temperature above 300 C. The alkali 'O1' caustic material causes the fats or fatty acids to saponify. The treatment also apparently causes many of the unsaturated materials to form saturated materials. The exact reaction which takes place to cause the transformation of the unsaturated material is not entirely clear. It may be that the double bond on the unsaturated material, such as oleic acid undergoes a cis-trans isomerization, or that the unsaturated materials are converted to,

shorter-chain materials along with such fragments as acetic acid and oxalic acid, or that poly-- merization occurs, or that some combination of the above-reactions takes place. I do not wish to be bound by any explanation of the processes,

but only by the process which results in the im-' 'provement.

The excess alkali remaining after the reaction of alkali with unsaturated material is neutralized by the addition of'a mineral acid as described above. The organic fatty acids are then sepa rated from the inorganic constituents. After the separation'of the fatty acids from the mixture,

the fattyacids are washed with water, after which they are dried and are converted to a metal soap of the fatty acid by reacting them with a stoichiometric equivalent of an alkali. The alkali 'is preferably a hydroxide of an alkali metal, such as sodium or potassium, or of an alkaline earth metal, such as calcium or barium.

in the presence of an alkali which is in excess of the treated materials, the stoichiometric excess may range as low as per cent by weight of the treated material. It is preferred, however, that the amount of caustic be at least per cent in excess of the amount stoichiometrically equivalent to the treated materials. The impure material-caustic mixture is generally heated at a temperature between about 300 C. and the is preferred, however, to heat the mixture at a temperature between about 310 C. and 350 C'.

for a period of from about 15 110,45 minutes.

Selected metal salts of fatty acids having between ten and twenty-four carbon atoms per molecule and prepared in the above-described;

manner may be incorporated in lubricating oils, such as mineral lubricating oils or polymer oils so as to produce a highly desirable grease. It is preferred to use metal salts of fatty acids which have afcarbon content of from fourteen to twenty carbon atoms per molecule. Generally between 5 and. 65 per cent by weight of a metal saltof a fatty acid, prepared as above described, may be incorporated in the lubricating oil at a temperature of between about C. and 250 C. It is preferred, however, to incorporate between 15 and 50 per cent by weight or an improved saturated soap, prepared by tne method of the instant invention, in a selected lubricating oil. Such amixture of a properly selected metal salt and a lubricating oil eating 0-1 mixture is preferably heated to a point.

where complete dispersion of the soapin oil is effected. It is then preierred to cool the soapoil mixture at a rapid rate so as to produce a gel. The temperature belowwhich the grease should be cooled is that at which solidification from a liquid to a gel occurs. Thistemperature is definitev and possibly related to the crystalline or collpidal structure of the metal salt, or at least it is a characteristic of the soap-oil mixture. It is not intended that the. temperature to which the mixture is cooled should be limited to any specifled temperature so long as it is below the gelation temperature. It is desired, however, that the time of cooling be as short as possible, generally within a periodof from. l0to 600 seconds. Longer periods. of time may be used for cooling these mixtures if desired, but it is preferred to cool the heated mixture to a. gel within aperiod of from 10 to 300 seconds. The cooled grease maybe worked to obtain the desired consistency.

Whena soap is to be treated in accordance with this invention, it is usually preferable to treat the soap with an alkali derived from the same metal as the soap. Sodium, potassium, calcium, and barium salts of fatty acids processedin the manner above described are amongithose salts which may be utilized to form desirable greases of this invention. Other metal salts may, however, be utilized to advantage. in thepreparation of such greases.

The advantages of preparing the metal salts by 4 the method of this invention are even more ap parent upon examination of the following examples. The specific reactants and specific conditions of reaction are presented as being typical and should not be construed to limit the invention unduly.

EXAMPLE I Sodium stearate containing as an impurity a scorching temperature of the treated materia 0 substantially equal amount of sodium oleate was treated with a quantity of alcoholic sodium hydroxide solution such that, on evaporation of the solvent, the molratio of sodium stearate to impurity to sodium hydroxide was approximately l:1:l.5. The alcoholic solution of sodium hydroxide was used-to obtain uniform distribution of the hydroxide and permit easy removal of the solvent.

The mixture was dried and then heated to between 310 C. and 320 C. for a period of about 20 minutes. The mixturewas; then cooled. and

was acidified with hydrochloric acid. The fatty acid was recovered and was washed with water, after which it was reactedwith sodium hydroxide. so as to resaponify. the fatty acid. Twenty per cent by weight of the resulting sodium soap. was dispersed in per centby weight of a lubricating oil, the properties of which are shown in Table II below. The dispersionofthe soap in thelubrieating oil was accomplished by heating. the mixture to about-220 C. and coolin rapidly. The resulting mass was .worked'in an A. S. T. M. grease worker (Precision Scientific: Motormatic Model) as describedin A. S-T. M, test D-21'1-44T. The consistency and w rkzstability of the resulting grease is set forth below in Table I as grease A.

' EXAMPLE II A portion. of. sodium stearate soap which was identical with, theoriginal soap in Example I was convertedtoagreaseby dispersing. 20 per centby weight in a. fraction of the. lubricating oil used. in Example I, the oil making up 80 per cent by weight. of the, soap-oil mixture. The mixture was heated. to. ab0ut-22.0. C. and. cooled rapidly. The resulting mass was worked inthe A. S. T. M. grease worker describedinExampleI. The re-.. sultsof the test made inthe greaseworker are recorded inTableI below forgrease B.

EXAMPLE III.

A sodium stearate soap fraction identical with that used in .Examplell andjto the, originaljsoap oilExample I was treated, with aquantityof aqueous sodium hydroxidesolution (2,5,.per cent, concentration). in a uantity sufficient that inthe final mixture, 1.5 moles of the ,sodium hydroxide. were present for each .molioffatty acid salt. The soap-alkali mixture, was. then .heated' at. 110, C; for about 30.minutesiwith constant stirring. The mixture was neutralized with hydrochloric acid; and, on cooling, free fatty. acids were removed. The solidifiediree fatty acids were liquefied by heating, after which they were washed with water and subsequently cooled. The solidified fatt'y acids were removed and dissolved in isopropylalcohol, neutralized with sodium hydroxide, and evaporated. to dryness. Twenty per cent by weight of the soap formed was dispersed in a fraction of the lubricating oil. used in Examples tween ten and twenty-four carbon atoms per molecule and containing as an impurity an unsaturated material selected from the group consisting of fats, fatty acids, and soaps of fatty acids, in the presence of an excess of an anhy- TABLE I I Comparison of stability of greases on working FM. Pi ojd Micropenetration on Working, Strokes ree Cl Soap Derived from Mixture Grease B Untreated, impure stear 45 336 365 385 Grease A Stearate treated with anhydrous hydroxide 47 176 202 24s s75 Grease C Stearate treated with aqueous hydrnxidp 10s 248 280 393 TABLE II dro-us alkali at a temperature between 300C. 20 and the scorching temperature of the treated Ph szcal constants 0 ml used m eparm rease y r f M g g material for between and 45 minutes, whereby said unsaturate material is decomposed and E P g VI D420 any saponifiable materials are saponified; reacting the resulting soap with a mineral acidto 1832 44.6 90-7 M748 8690 l1berate free organic acids; recoverin organic acid materials from the resulting mixture; wash- Comparison of..the micropenetration readings resulting from the tests made with the greases of Examples I, II, and III clearly shOWs that the grease formed from the fatty acid which was treated with the anhydrous sodium hydroxide had far greater consistency than either of the other two greases.

As will be evident to those skilled in the art, various modifications can be made in the selection of the solvent for the base solution used in treating the'soap or the materials which are saponifiable by treatment with a base solution. It is preferred, however, that the selected alkali or base have a similar basicity to the base of the soap treated. Other modifications may be made in the oil used as the dispersion agent for the production of a grease. It is believed that various other modifications of this invention can" be made or followed in the light of the foregoing disclosure and discussion without departing from the spirit or scope of the disclosure or from the scope of the claims.

I claim: 7

1. An improved method for making grease which comprises the steps of improving at least one material selected from a group of saturates consisting of fats, fatty acids, and soaps of fatty acids, which saturates contain as impurities unsaturates of a chemical type similar to said saturates, by heating at least one of said saturates having between ten and twenty-four carbon atoms per molecule in the presenceof an excess of an anhydrous alkali at a temperature between 300 C. and the scorching temperature of the saturate material for between 15 and 45 minutes,wherebysaid unsaturates are decomposed and saponifiable materials are saponified; reacting resulting soap with a mineral acid to liberate free organic acids; recovering organic acid materials from said resulting mixture; washing said organic acid materials; resaponifying said organic acid materials by heating with a stoichiometric amount of a metal base; incorporating resulting soap in oil by heating and rapidly cooling said organic materials; resaponifying said organic acid materials by heating with a stoichiornetric amount of a metal base to form a soap; incorporating between 5 and 65 per cent by weight of said soap in between 35 and per cent by weight of a lubricating oil at a temperature of between C. and 250 0.; cooling said soap in an oil mixture to form a gel'within a period of from 10 to 600 seconds; and working said gel to the desired consistency.

3. The method of claim 2, wherein said metal base is derived from the same metal as said) saturated soap.

4. A method of producing an improved grease which comprises the steps of heating at least one saturated fatty acid having between ten and twenty-four carbon atoms per molecule and containing as an impurity at least one unsaturated material selected from the group consisting of fats, fatty acids, and soaps of fatty acids, in the presence of an excess of an anhydrous alkali at a temperature between 300 C. and the scorching temperature of the treated material for between 15 and 45 minutes, whereby said unsaturate material isdecomposed and any sap-onifiable materials are saponified; reacting the resulting soap with a mineral acid to liberate free organic acids, recovering organic acid materials from the resulting mixture; washing said organic materials; resaponifying said organic acid materials by heating with a stoichiometric amount of a metal base to form a soap; incorporating between 5 and 65 per cent by weight of said soap in be-' tween 35 and 95 per cent by weight of a lubricating oil at a temperature of between 170 C. and 250 C.; cooling said soap in an oil mixture to form a gel within a period of from 10 to 600 seconds; and working said gel to the desired consistency.

5. A method of producing an improved grease which comprises the steps of heating at least one saturated fat having between ten and twentyfour carbon atoms per molecule and containing as impurities at least one unsaturated material selected from the group consisting of fats, fatty acids, and soaps of fatty acids, in the presence of an excess of an anhydrous alkali at a temperature between 300 C. and the scorching temperature of the treated material for between 15 and 45 remotes; whereby said.- n atur e aterial. is; decomposed-and; any saponiiiable-,materials are.-;

saponified-y reacting theresulting; soapwith, a

mineralacid to liberate free: organic; acids; re

coyerin or anicacid materials from the. resulting mixture; washing said organic materials; resaponifying said organic acid materials by heating with a stoichiometric amount of a metalzbasi?v to form a soap; incorporating between.5 and 65.

per cent by weight of said soap in between 35 .and

95 per cent by weight of a lubricating oil at,a..

temperature of between 170 C. and 250 0,; cool ing said soap in an oil mixture, to form a gel within a period of from to 600 seconds; and working said gel to the desired consistency,

6. A method of producing an improved grease which comprises the steps of heating at least" one saturated material having-between tenand twenty-four; carbon atoms per; molecule which saturated material is? selected from, the" group consisting of fats, fatty: acids; and soaps of fatty acids and containing as an impurity'therein at least one unsaturated material selected from the group consisting of fats, fatty acids, and soaps of saponifiable materials aresaponified; reacting u theresulting soap with a mineral acid to liberate free organic-acids; recovering organic acid materials from the resulting mixture; washing said organic, materials; resaponifying said organic acid materials byheatingwith a-stoichiometric amount ofametal base to form a soap; incorporating between 5 and 65 percent by weight of said soap in between -and 95-per cent by weight of said lubricating oil at a temperature of between 50 C. and 250 0.; cooling said soap-oil mixtureto form a gel within a period of from 10 to 600 seconds; and working saidgel to the desired consistency.

7. A; method of producing an improved grease whichcomprises the steps of heating at, least i one saturated material having between ten and twenty-four carbon atoms per molecule. which saturated, material is selected from the group consisting of fats, fatty acids, and soapsof fatty acids and containing as an impurity therein at least one unsaturated material selected from the roup;- ccnsis ing of. rats ra tan acid nd. cars, or; fatty acids, in ,the-presem of anexcess of, an, anhydrous alkali, atatemperature between .300f" C.. and thescorching temperature .of the treated material for between 15 and minutes,.whereby unsaturate materials are decomposed and any saponifiable materials are saponified; reacting theresultingsoapwith amineral acid to liberate free organic acids; recovering organic, acid materials from the resulting mixture; washing said organic materials, resaponifyingsaid or anic acid materials by heating with a stoichiometric amount, of a metal base to form, asoap; incorporating between:15 and, per cent by weight of said soap in between 50 and per cent by weight", of said lubricating oilat a temperaturebetween,

50- C; and 250- C.; cooling. said soap-oilmixture to-form a gel within a period of from 10 to 300..

seconds; and working said: gel to the desired consistency.

8; The method of claim 6, wherein saidsaturated material is a sodium soap; said alkali-soap mixture is heated at a temperature between 310 C. and 350 C. and said metal baseis an aqueous solution of sodium hydroxide.

REFER NCE ITED;

The following references are of record in thefile of this patent:

UNITED. STATES PATENTS.

Number Name Date- 1,429,114 Stiepel Sept. 12, 1 922, 1,598,225 Walker, Aug. 31, 1926 1,973,537 Miller et a1. Sept. 11, 1934 2,070,014 V ..Feb. 9, 1937 2,428,123 Morgan et al. H Sept. 30,1947

OTHER REFERENCES Spitzer et al.: Conjugation rnr-yln 'ou Fatty. Acids, reprint of articles in American PaintJour- Ha December 1 an L Z; 1,9A1,,page.-1. 

1. AN IMPROVED METHOD FOR MAKING GREASE WHICH COMPRISES THE STEPS OF IMPROVING AT LEAST ONE MATERIAL SELECTED FROM A GROUP OF SATURATES CONSISTING OF FATS, FATTY ACIDS, AND SOAPS OF FATTY ACIDS, WHICH SATURATES CONTAIN AS IMPURITIES UNSATURATES OF A CHEMICAL TYPE SIMILAR TO SAID SATURATES, BY HEATING AT LEAST ONE OF SAID SATURATES HAVING BETWEEN TEN AND TWENTY-FOUR CARBON ATOMS PER MOLEULE IN THE PRESENCE OF AN EXCESS OF AN ANHYDROUS ALKALI AT A TEMPERATURE BETWEEN 300* C. AND THE SCORCHING TEMPERATURE OF THE SATURATE MATERIAL FOR BETWEEN 15 AND 45 MINUTES, WHEREBY SAID UNSATURATES ARE DECOMPOSED AND SAPONIFIABLE MATERIALS ARE SAPONIFIED; REACTING RESULTING SOAP WITH A MINERAL AID TO LIBERATE FREE ORGANIC ACIDS; RECOVERING ORGANIC ACID MATERIALS FROM SAID RESULTING MIXTURE; WASHING SAID ORGANIC ACID MATERIALS; RESAPONIFYING SAID ORGANIC ACID MATERIALS BY HEATING WITH A STOICHIOMETRIC AMOUNT OF A METAL BASE; INCORPORATING RESULTING SOAP IN OIL BY HEATING AND RAPIDLY COOLING THE SOAP-OIL MIXTURE TO FORM A GEL. 